THE NERVOUS SYSTEM II pp. 1003-1015

FUNCTION network of neurons that communicate and control the body through electrical impulses Includes neurons, brain and spinal cord

Synapse Synapse: point where an axon and dendrite meet Neurotransmitter – chemical that carries the message across the synapse

NERVE IMPULSES Membrane potential- difference in charge inside and outside cell Resting potential: inactive cell due to “negatively” charged inside as compared to outside

NERVE IMPULSES Action potential (electrical signals) When dendrite is stimulated, NA+ channels along the axon open making inside positive

NERVE IMPULSES Action potential When dendrite is stimulated, NA+ channels along the axon open making inside positive As soon as they open, K+ channels pump K+ out restoring a negative resting potential.

NERVE IMPULSES When the impulse reaches terminal neurotransmitters are released into synaptic cleft This causes the next neuron to become more positive and the action potential continues or stimulates a muscle or gland

Effect of drugs on the nervous system

Drugs may…. Prevent re-uptake of neurotransmitters Over stimulation of nervous system Mimicking neurotransmitters

Two parts to Nervous System

CENTRAL NERVOUS SYSTEM (CNS) Receives , interprets, processes, and creates messages Parts Brain – control center Spinal cord –link between brain and Peripheral NS.

PERIPHERAL NERVOUS SYSTEM PNS Carries impulses (messages) to and from the CNS. Motor division 1. somatic nervous system (voluntary): transmits impulses to and from skeletal muscle

2. Autonomic nervous system (involuntary) – controls glands, internal organs, and other smooth muscle tissue.